1. Field of the Invention
This invention relates to high voltage solid state switches, and in particular, to a high voltage solid solid state switch in which a pair of series connected field effect transistors are turned on by a photovoltaic generator and turned off by an opto-coupler. The invention is particularly suited for use in automatic test equipment for the testing of integrated circuits.
2. Description of the Prior Art
In automatic test equipment for the testing of integrated circuits and other electronic components, pin electronics interface circuits are coupled to the pins or other nodes of an electronic device being tested. Through the pins, stimuli signals are applied to the device under test, and output signals from the device under test are detected and measured. Usually the stimuli signals represent logic states or analog voltages or currents which are desired to be impressed upon the pins of the device under test as a parallel pattern, with the resulting output signals checked in parallel. In typical prior art systems the switching of drivers, comparators, and other circuits to the pins of the device being tested has been accomplished using mechanical relays, for example, a three Form A relay.
The use of relays for switching in automatic test equipment results in a number of disadvantages, primarily because relays operate at relatively slow switching speeds. The slow switching speed, on the order of hundreds of microseconds, results in substantial dead time for the automatic test equipment. In some state of the art test equipment about one-half of the tester dead time is spent waiting for relays to close.